The diagnostic value of dynamic contrast-enhanced MRI for thyroid tumors

Background and purpose

The exact place for dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in the diagnosis and management of thyroid tumors is still under debate. We performed the study to analyze and compare the parameters generated from DCE-MRI for thyroid lesions.

Materials and methods

For each thyroid lesion, time intensity curves (TIC), time of peak enhancement (T_peak), maximum enhancement ratio (ER_max) and maximum rise slope (Slope_max) were plotted and calculated. Receiver operator characteristics (ROC) analysis was conducted to assess the diagnostic ability and appropriate cut-off value. The area under the ROC curve (AUC) and the confidence intervals (CIs) were also assessed.

Results

Forty-two patients were consecutively included. All 21 lesions demonstrated the rapid inflow and washout pattern (type-I) were benign. The 12 cases with delayed inflow pattern (type-III) were all malignant. When compared with the benign lesions, the thyroid carcinoma showed significantly lower Slope_max and higher T_peak (P < 0.05). No statistical difference of ER_max was found between malignant and benign ones (P = 0.15). The AUC of ER_max, Slope_max and T_peak in differentiating benign thyroid lesions from malignant ones were 0.63, 0.93and 1, respectively. The ER_max cut-off value of 73.86 (sensitivity, 71.4%; specificity, 64.3%), Slope_max cut-off value of 2.4126 (sensitivity, 92.9%; specificity, 82.1%) and T_peak value of 28 (sensitivity, 100%; specificity, 100%) offered the best diagnostic performances.

Conclusions

DCE-MRI, especially the pattern of TIC and the value of Slope_max and T_peak, could be helpful in differentiating thyroid carcinoma from benign thyroid lesions.     

Assessment of dynamic contrast-enhanced magnetic resonance imaging in the differentiation of malignant from benign orbital masses

Objective

Dynamic contrast enhanced MR imaging (DCE-MRI) allows imaging of the physiology of the microcirculation. The purpose of this study was to determine the diagnostic efficacy of time intensity curve (TIC) and DCE parameters for characterization of orbital masses.

Methods

Fifty-nine patients with untreated orbital lesions underwent DCE-MRI before surgery. For each lesion, peak height (PH), maximum enhancement ratio (ER_max), time of peak enhancement (T_peak) and maximum rise slope (Slope_max) were plotted and calculated. Receiver operator characteristics (ROC) analysis was conducted to assess the appropriate cut-off value.

Results

All 26 lesions that demonstrated persistent pattern (type-I) TICs were benign. Most of the masses with the washout pattern (type-III) TIC were malignant (10/14), including lymphoma (n = 6) and melanoma (n = 4). The Slope_max of benign lesions was statistically lower than malignant ones, while the ER_max and T_peak values of benign lesions were significantly higher. No statistical difference was found in PH (P = 0.121). The AUC for ER_max, T_peak and Slope_max in differentiating benign orbital lesions from malignant ones were 0.683, 0.837 and 0.738, respectively. In the three DCE parameters, Slope_max cut-off value of 1.10 provided the highest sensitivity of 93.8%; however, the corresponding specificity was low (58.1%). The ER_max cut-off value of 1.37 and T_peak cut-off value of 35.14 respectively offered the best diagnostic performances.

Conclusion

DCE-MRI, especially the qualitative TIC pattern and quantitative value of Slope_max, ER_max and T_peak, could be a complementary investigation in distinguishing malignant orbital tumor from benign ones.     

Quantitative analysis of liver function using superparamagnetic iron oxide- and Gd-EOB-DTPA-enhanced MRI: comparison with Technetium-99m galactosyl serum albumin scintigraphy

Purpose

To examine whether or not the parameters regarding the signal intensity of the liver parenchyma on superparamagnetic iron oxide (SPIO)- and gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced MRI are correlated with the parameters of Technetium-99m galactosyl serum albumin (^99mTc-GSA) scintigraphy.

Materials and methods

This retrospective study consisted of 55 and 33 patients who underwent SPIO- and Gd-EOB-DTPA-enhanced MRI in addition to ^99mTc-GSA scintigraphy, respectively. For each patient, we calculated Pre R2* and Pre R2, which are equivalent to R2* (=1/T2*) and R2 (=1/T2) values of the liver parenchyma; ΔR2* and ΔR2, which represent differences in R2* and R2 values of the liver parenchyma before and after administration of SPIO; and the increase rates of both the liver-to-spleen signal intensity ratio (LSR) and the liver-to-major psoas muscle signal intensity ratio (LMR) on the hepatobiliary phase compared with the precontrast image. For ^99mTc-GSA scintigraphy, the receptor index LHL15 and the blood clearance index HH15 were recorded.

Results

Regression analysis showed a moderate correlation between Pre R2* and LHL15 (P < 0.05). Mild to moderate correlations were also obtained between any combination of ΔR2* and ΔR2 on the one hand, and LHL15 and HH15 on the other (P < 0.05). There were moderate correlations between any combination of increase rates of LSR and LMR on the one hand, and LHL15 and HH15 on the other (P < 0.05–0.001).

Conclusion

Pre R2*, ΔR2*, ΔR2 and the increase rates of LSR and LMR could be used as quantitative indicators of liver function.     

Assessment of colorectal hepatic metastases by quantitative T2 relaxation time

Aim

To determine the T₂ relaxation time of colorectal hepatic metastases and changes in T₂ relaxation times following chemotherapy.

Materials and methods

42 patients with 96 hepatic colorectal metastases underwent baseline MRI. Axial T₁, T₂ and multi-echo GRASE sequences were acquired. ROIs were drawn on T₂ relaxation maps, obtained from GRASE images, encompassing metastasis and normal liver to record T₂ relaxation time values. In 11 patients with 28 metastases, MRI was repeated using same protocol at 6 weeks following chemotherapy. The median pre-treatment T₂ values of metastases and normal liver were compared using the Mann–Whitney test. The pre- and post-treatment median T₂ values of metastases were compared using the Wilcoxon–Rank test for responding (n = 16) and non-responding (n = 12) lesions defined by RECIST criteria. The change in T₂ values (ΔT₂) were compared and correlated with percentage change in lesion size.

Results

There was no difference in the pre-treatment median T₂ of metastases between responding (67.3 ± 8.6) and non-responding metastases (71.4 ± 16.5). At the end of chemotherapy, there was a decrease in the median T₂ of responding lesions (61.6 ± 12.6) p = 0.83, and increase in non-responding lesions (76.2 ± 18.4) p = 0.03, but these were not significantly different from the pre-treatment values. There was no significant difference in ΔT₂ of responding and non-responding lesions (p = 0.18) and no correlation was seen between size change and ΔT₂ (coefficient = 0.3).

Conclusion

T₂ relaxation time does not appear to predict response of colorectal liver metastasis to chemotherapy.     

Effect of duration of scan acquisition on CT perfusion parameter values in primary and metastatic tumors in the lung

Objectives

To assess the effect of acquisition duration (T_acq) and pre-enhancement set points (T₁) on computer tomography perfusion (CTp) parameter values in primary and metastatic tumors in the lung.

Materials and methods

24 lung CTp datasets (10 primary; 14 metastatic), acquired using a two phase protocol spanning 125 s, in 12 patients with lung tumors, were analyzed by deconvolution modeling to yield tumor blood flow (BF), blood volume (BV), mean transit time (MTT), and permeability (PS) values. CTp analyses were undertaken for the reference dataset (i.e., T₁ = t₀) with varying T_acq from 12 to 125 s. This was repeated for shifts in T₁ (±0.5 s, ±1.0 s, ±2.0 s relative to the reference at t₀). Resultant CTp values were plotted against T_acq; values at 30 s, 50 s, 65 s and 125 s were compared using linear mixed model.

Results

All CTp parameter values were noticeably influenced by T_acq, with generally less marked changes beyond 50 s, and with no difference in behavior between primary and secondary tumors. Apart from BV, which attained a plateau at approximately 50 s, the other three CTp parameters did not reach steady-state values within the available 125 s of data, with values at 30 s, 50 s and 65 s significantly different from 125 s (p < 0.004). Shifts in T₁ also affected the CTp parameters values, with positive shifts having greater impact on CTp values than negative shifts.

Conclusion

CTp parameter values derived from deconvolution modeling can be markedly affected by T_acq, and pre-enhancement set-points. 50 s acquisition may be adequate for BV, but longer than 125 s is probably required for reliable characterization of the other three CTp parameters.     

Evaluation of T1ρ as a potential MR biomarker for liver cirrhosis: Comparison of healthy control subjects and patients with liver cirrhosis

Objectives

The purpose of this study was to compare mean liver T_1ρ values in patients with liver cirrhosis and healthy control subjects in order to evaluate T_1ρ as a potential MR biomarker for liver cirrhosis.

Materials and methods

Ten healthy control subjects (mean age 42.7 years; 6 female, 4 male) and 21 patients with clinically diagnosed liver cirrhosis (mean age 56.5 years; 5 female, 16 male) were examined at 1.5 T (Magnetom Avanto, Siemens). T_1ρ-weighted images were acquired using a 2D TurboFLASH sequence (TR/TE 3/1.31 ms, FA 8°, FoV 309 × 380 mm, resolution 2 × 2 × 6 mm, acquisition time 15 s, slice thickness 6 mm) with spin-lock preparation. T_1ρ maps were calculated from five breath-hold measurements, performed with different spin-lock times (4, 8, 16, 32 and 48 ms). Mean liver T_1ρ values of healthy control subjects and patients with liver cirrhosis were calculated and compared using Student t-test. In addition, a receiver operating characteristic (ROC) curve analysis was performed to evaluate the utility of mean liver T_1ρ values for the prediction of liver cirrhosis.

Results

Mean liver T_1ρ values in patients with liver cirrhosis (57.4 ± 7.4 ms) were significantly higher than those of healthy subjects (47.8 ± 4.2 ms; p = 0.0007). According to the ROC analysis at a threshold value of 50.1 ms the sensitivity and specificity of mean liver T_1ρ in predicting liver cirrhosis were 90.5% and 90%, respectively. The area under the ROC curve was 0.90.

Conclusion

Mean liver T_1ρ values in patients with liver cirrhosis were significantly higher than those in healthy subjects suggesting a potential role of liver T_1ρ as a MR biomarker for liver cirrhosis.     

Perfusion characteristics of parotid gland tumors evaluated by contrast-enhanced ultrasound

Purpose

Contrast enhanced ultrasound (CE-US) is a promising imaging modality for non-invasive analysis of parotid gland lesions because their vascularisation differs from normal gland tissue. This clinical study should further investigate CE-US as a diagnostic tool for parotid gland tumors.

Materials and methods

39 patients underwent CE-US measurements after intravenous application of a contrast agent (SonoVue, Bracco, Italy) before surgical tumor resection. Time–intensity curves gradients were calculated and parameters of intratumoral microcirculation were analysed. The vascularisation parameters were compared among the different tumor entities as defined per definitive histological diagnosis.

Results

Histological analyses revealed 17 pleomorphic adenoma, 15 cystadenolymphoma and 7 malignoma. A significant difference of area below intensity time curve (AUC) and mean transit time (MTT) was measured in the malignant lesions compared to benign tumors (p < 0.05). A significant difference of AUC and maximum of signal increase (ΔSI_max) for pleomorphic adenoma versus cystadenolymphoma was found (p < 0.05).

Conclusion

CE-US seems to be a quantitative and independent method for the assessment of malign and benign parotid gland tumors. Further studies and clinical experience will have to validate this method as a reliable diagnostic tool that facilitates preoperative planning.     

Comparison of Conventional and Cone-Beam CT for Monitoring and Assessing Pulmonary Microwave Ablation in a Porcine Model

Purpose

To compare cone-beam computed tomography (CT) with conventional CT for assessing the growth and postprocedural appearance of pulmonary microwave ablation zones.

Comparison of axial, coronal, and primary 3D review in MDCT colonography for the detection of small polyps: a phantom study

Purpose

The purpose of this phantom study is to compare the influence of the reading technique (axial images alone in comparison to 3D endoluminal, coronal, and combined 2D/3D review methods) on the sensitivity and inter-reader variability with MDCT colonography for the detection of small colonic polyps.

Methods

An anthropomorphic pig colon phantom with 75 randomly distributed simulated small polyps of 2–8 mm size, was distended with air and scanned in a water phantom using multidetector-row CT with 4 mm × 1 mm collimation. Three radiologists rated the presence of polyps on a five-point scale. Performance with axial sections alone was compared to the performance with coronal sections, virtual endoscopy (VE), and a combined 2D/3D approach. We calculated sensitivities for polyp detection and used ROC analysis for data evaluation.

Results

There was no significant difference between the mean area under the curve (A_z) for axial images and VE (A_z = 0.934 versus 0.932), whereas coronal images were significantly inferior (A_z = 0.876) to both. The combined 2D/3D approach yielded the best results, with an A_z of 0.99. Differences in sensitivity between individual readers were significant in axial images (sensitivity, 75–93%, p = 0.001) and coronal images (sensitivity, 69–80%, p = 0.028), but became non-significant with VE (83–88%, p = 0.144) and the combined 2D/3D approach (95–97%, p = 0.288).

Conclusion

Evaluation of axial sections alone leads to significant differences in detection rates between individual observers. A combined 2D/3D evaluation improves sensitivities for polyp detection and reduces inter-individual differences to an insignificant level.     

The low attenuation area on dual-energy perfusion CT: correlation with the pulmonary function tests and quantitative CT measurements

Purpose

To retrospectively investigate the distribution of the low attenuation area (LAA) on dual energy perfusion CT (DEpCT) in comparison with the results of pulmonary function tests (PFTs) and quantitative CT measurements.

Materials and methods

Twenty-eight patients (15 male and 13 female; mean age: 62.21 years) underwent DEpCT and PFTs within a 1-month interval. The ranges of the LAA on DEpCT were classified into six groups with attenuation values of 0–3, 0–5, 0–8, 0–10, 0–13 and 0–15 HU and the ratios of LAA in each group were compared with the percentage of forced expiratory volume in the 1st second (%FEV_1.0), FEV_1.0/forced vital capacity (FEV_1.0/FVC) and the relative area of the lung with attenuation coefficients lower than −950 HU (RA₋₉₅₀).

Results

The LAAs on the DEpCT images were significantly correlated with the RA₋₉₅₀, %FEV_1.0 and FEV_1.0/FVC, and the regression analysis showed that the best values of LAA on DEpCT were 0–10 HU with RA₋₉₅₀ (r = 0.63), 0–8 HU with %FEV_1.0 (r = −0.52) and 0–8 HU with FEV_1.0/FVC (r = −0.61) per patient.

Conclusion

The iodine disturbance on DEpCT had a moderate correlation with the results of the PFTs and RA₋₉₅₀, but further examination would be needed for evaluation of iodine distribution.     

Contrast-enhanced dynamic and diffusion-weighted MR imaging at 3.0 T to assess aggressiveness of bladder cancer

Background

Diffusion weighted magnetic resonance imaging (DWI) and dynamic contrast-enhanced (DCE) MRI have been considered useful for pathological staging and histological grading in bladder cancer. To our knowledge, no study has combined the two imaging modalities together to assess aggressiveness of bladder cancer.

Objective

To assess the clinical aggressiveness of bladder cancer with DCE MRI and DWI at 3.0 T.

Materials and methods

A total of 59 patients with 69 pathologically confirmed tumor lesions were included in this study. All patients underwent MR examination at 3.0 T basing on DWI and DCE imaging. Tumor staging and histological grade were evaluated. The aggressiveness of bladder cancer was classified as low-, intermediate-, or high-aggressiveness according to its pathological phenotype. Apparent diffusion coefficient (ADC) value and semi-quantitative parameters (wash-in rate and wash-out rate) were determined. The correlation between clinical aggressiveness and ADC value, wash-in rate and wash-out rate were analyzed. In addition, the diagnostic accuracy of the diffusion and semi-quantitative parameters were estimated using receiver operating characteristic curve (ROC).

Results

Aggressiveness of bladder cancer is negatively correlated with ADC value (r = −0.705, p < 0.0001) and wash-out rate (r = −0.719, p < 0.0001). The tumor ADC value is positively correlated with wash-out rate (r = 0.555, p < 0.0001). The diagnostic specificity and accuracy using tumor ADC value and wash-out for the tumor with size <24 mm were better than that tumors with size ≥24 mm. The sensitivity, specificity and accuracy of ADC and wash-out rate in combination in diagnosis of bladder cancer aggressiveness were 96.7%, 94.9% and 95.7%, respectively. ROC curve revealed the diagnostic performance of aggressiveness of bladder cancer using ADC value and wash-out rate were 0.928 (cut-off value: 0.905 × 10⁻³ mm²/s) and 0.891 (cut-off value: 0.685 min⁻¹), respectively.

Conclusion

ADC and wash-out rate derived from DWI and DCE-MRI at 3.0 T have good potential to assess the aggressiveness of bladder cancer and the accuracy was greater for ADC than for semi-quantitative parameters.     

The accuracy of ultrasonography in the preoperative diagnosis of cervical lymph node metastasis in patients with papillary thyroid carcinoma: A meta-analysis

Background

Ultrasonography has been proposed to enhance preoperative assessment of cervical lymph node status in patients with papillary thyroid carcinoma (PTC). Management is most controversial for patients with a clinically negative (cN0) neck. We aimed to evaluate the diagnostic properties of ultrasonography in the detection of cervical lymph node metastasis in patients with PTC.

Materials and methods

Studies evaluating the diagnostic accuracy of Ultrasonography in the diagnosis of cervical lymph node metastasis in patients with PTC were systematically searched for in the MEDLINE, EMBASE, Cancerlit and Cochrane Library and other database from January 1995 to November 2010. Two reviewers independently abstracted data including research design, sample size, imaging technique and technical characteristics, method of image interpretation. By patient-based and region- or node-based data analyses, we determined pooled sensitivities and specificities across studies, and constructed summary receiver operating characteristic curves, and area under summary receiver operating characteristic curves were calculated.

Results

The pooled patient-based sensitivity for ultrasonography was 0.72 (95% CI, 0.46–0.88), specificity was 0.98 (95% CI, 0.84–1.00), and the area under the curve (AUC) was 0.94 (95% CI, 0.92–0.0.96). The pooled region- or node-based sensitivity for ultrasonography was 0.63 (95% CI, 0.47–0.76), specificity was 0.93 (95% CI, 0.73–0.99), and the AUC was 0.81 (95% CI, 0.77–0.84). For lesion-based analysis, the subgroup of lateral compartment lymph node involvement was found to have the highest sensitivity (0.72, 95% CI 0.68–0.75) and specificity (0.97, 95% CI 0.93–0.99) among the studies (p < 0.05). Study sensitivity was not correlated with the prevalence of cervical lymph node metastasis (patient-based: R² = 0.0196, p = 0.7915; region- or node-based: R² = 0.3835, p = 0.1381).

Conclusions

We conclude that preoperative ultrasonography is a good technique for the preoperative lymph node staging of PTC and is helpful for detecting metastatic cervical lymph nodes at the lateral group. High-quality prospective studies regarding ultrasonography in the evaluation of cervical lymph node status in patients with PTC are still needed to be conducted.     

Nutcracker and SMA syndromes: What is the normal SMA angle in children?

Objective

The nutcracker and superior mesenteric artery (SMA) syndromes are rare conditions where the left renal vein or duodenum may be compressed by an unusually acute angle between the SMA and aorta, although the normal angle in children is unknown. We measured the SMA angle to define the normal range in children.

Methods

We retrospectively measured SMA angles, left renal vein (LRV) distance, and duodenal distance (DD) in 205 consecutive pediatric abdominal CT. Total and visceral intra-abdominal fat at the level of the umbilicus were also assessed.

Results

Mean SMA angle was 45.6 ± 19.6° (range 10.6–112.9°), mean LRV distance was 8.6 ± 3.9 mm (range 2.0–28.6 mm) and mean DD was 11.3 ± 4.8 mm (range 3.6–35.3 mm). There was a significant but weak correlation between %visceral fat volume (%VF) and SMA angle (R = 0.30; p < 0.001), LRV distance (R = 0.37, p < 0.001) and DD (R = 0.32; p < 0.001).

Conclusion

There is a wide range of SMA angle, LRV and DD in normal children, which correlated weakly with visceral fat volume. Using a definition of SMA angle <25° would diagnose 9.3% of asymptomatic children with nutcracker syndrome, and using a DD definition of <8 mm would diagnose 20% with SMA compression. Our findings suggest exercising caution when attributing these rare syndromes to an absolute SMA angle.     

MRI evaluation of residual tumor size after neoadjuvant endocrine therapy vs. neoadjuvant chemotherapy

Aim

To investigate if there is any difference in evaluation of residual tumor size after neoadjuvant chemotherapy (NAC) and neoadjuvant endocrine therapy (NAE).

Methods

Seventy-eight tumors in 57 patients were prospectively enrolled. Residual tumor sizes in contrast-enhanced MRI after NAC and NAE were compared with those measured on surgical specimen by using linear regression analyses. The line slope values >1 indicates overestimation by MRI. Differences in types of shrinkage patterns: concentric shrinkage (CS) and dendritic shrinkage (DS) were also investigated.

Results

Fifty lesions were treated with NAC and 28 lesions were treated with NAE. Shrinkage patterns were CS in 33 lesions and in 45 lesions. The slopes values were 0.75 (R = 0.92) and 0.70 (R = 0.90) for NAC and NAE, respectively, and no significant difference was observed (p = 0.46). However, they were 1.02 (R = 0.92) and 0.68 (R = 0.92), respectively for CS and DS with significant difference (p < 0.01). The difference between CS and DS was found only in a subgroup with size by MRI >20 mm.

Conclusion

Contrast enhanced MRI enabled fairly accurate measurement in NAE as well as in NAC.     

Can pretreatment ADC values predict recurrence of bladder cancer after transurethral resection?

Objective

The aim of this retrospective study was to investigate the association between the pretreatment apparent diffusion coefficient (ADC) value and recurrence of bladder cancer after transurethral resection.

Methods

Patients with superficial bladder cancer were identified. Mean ADC values of the tumors were compared between patients with and without recurrence following trans-urethral resection. A receiver–operator characteristic curve was used for determining the optimal cutoff ADC value. Univariate and multivariate analyses were used to determine the effect of ADC values and other factors.

Results

With a mean follow-up period of 25 months, bladder cancer recurred in 14 of 44 patients (32%). The mean ADC value of tumors in patients with recurrence was lower than in those without recurrence (1.08 mm²/s vs. 1.28 × 10⁻³ mm²/s; p = 0.003). The optimal cutoff ADC value for predicting recurrence was determined to be 1.12 × 10⁻³ mm²/s. A modest and significant negative correlation was observed between the ADC values and tumor size (r = −0.436, p = 0.008). After adjustment for size and risk groups, an ADC value equal to or less than the optimal cutoff remained a significant predictor of recurrence (odds ratio 6.3, 95% CI 1.23–32.2, p = 0.027).

Conclusion

Pretreatment ADC values may be an independent predictor of bladder cancer recurrence.     

Clinical evaluation of PET image reconstruction using a spatial resolution model

Purpose

PET image resolution is variable across the measured field-of-view and described by the point spread function (PSF). When accounting for the PSF during PET image reconstruction image resolution is improved and partial volume effects are reduced. Here, we evaluate the effect of PSF-based reconstruction on lesion quantification in routine clinical whole-body (WB) PET/CT imaging.

Materials and methods

41 oncology patients were referred for a WB-PET/CT examination (Biograph 40 TruePoint). Emission data were acquired at 2.5 min/bed at 1 h pi of 400 MBq [18F]-FDG. Attenuation-corrected PET images were reconstructed on 336 × 336-matrices using: (R1) standard AW-OSEM (4 iter, 8 subsets, 4 mm Gaussian) and (R2) AW-OSEM with PSF (3 iter, 21 subsets, 2 mm). Blinded and randomised reading of R1- and R2-PET images was performed. Individual lesions were located and counted independently on both sets of images. The relative change in PET quantification (SUV_max, SUV_mean, volume) of lesions seen on R1 and R2 is reported as (R2 − R1)/R1. Furthermore, SUV_max and SUV_mean was measured for a 3 cm spherical norm region in the right lobe of the healthy liver for R1 and R2.

Results

Clinical reading revealed 91 and 103 positive lesions for R1 and R2, respectively. For all lesions SUV_max (R2) was higher than SUV_max (R1). Regression analysis indicated that the relative increase in SUV_max (and SUV_mean) decreased with lesion size, whilst it increased with increasing radial distance from the centre of the field of view (FOV). There was no significant difference in SUV_mean in homogenous liver tissue between R1 and R2.

Conclusion

In whole-body FDG-PET/CT using routine clinical protocols, PSF-based PET reconstruction increases lesion detection and affects SUV_max measurements compared to standard AW-OSEM PET reconstruction.     

MR spectroscopy of liver in overweight children and adolescents: investigation of ¹H T₂ relaxation times at 3T

Objective

The objective was to investigate T₂ relaxation values and to optimize hepatic fat quantification using proton MR spectroscopy (¹H MRS) at 3 T in overweight and obese children and adolescents.

Subjects

The study included 123 consecutive children and adolescents with a body mass index above the 97th percentile according to age and sex.¹H MR spectroscopy was performed at 3.0 T using point resolved spectroscopy sequence with series TE. T₂ relaxation values and hepatic fat content corrected for the T₂ relaxation effects were calculated.

Results

T₂ values for water ranged from 22 ms to 42 ms (mean value 28 ms) and T₂ values for fat ranged from 36 ms to 99 ms (mean value 64 ms).Poor correlation was observed: (1) between T₂ relaxation times of fat and T₂ relaxation times of water (correlation coefficient r = 0.038, P = 0.79); (2) between T₂ relaxation times of fat and fat content (r = 0.057, P = 0.69); (3) between T₂ relaxation times of water and fat content (r = 0.160, P = 0.26).Correlation between fat peak content and the T₂ corrected fat content decreased with increasing echo time TE: r = 0.97 for TE = 45, r = 0.93 for TE = 75, r = 0.89 for TE = 105, P < 0.0001.

Conclusion

¹H MRS at 3 T is an effective technique for measuring hepatic fat content in overweight and obese children and adolescents. It is necessary to measure T₂ relaxation values and to correct the spectra for the T₂ relaxation effects in order to obtain an accurate estimate of the hepatic fat content.     

Prognostic value DCE-MRI parameters in predicting factor disease free survival and overall survival for breast cancer patients

Purpose

The aim of the study is to assess the predictive power of DCE-MRI semi-quantitative parameters during treatment of breast cancer, for disease-free (DFS) and overall survival (OS).

Materials and methods

Forty-nine women (age range, 28–84 years; mean, 50.6 years) with breast cancer underwent dynamic contrast enhancement MRI at 1.0 T imaging, using 2D FLASH sequences. Time intensity curves (TICs) were obtained from the regions showing maximal enhancement in subtraction images. Semi-quantitative parameters (TICs; maximal relative enhancement within the first minute, E (max/1); maximal relative enhancement of the entire study, E_max; steepest slope of the contrast enhancement curve; and time to peak enhancement) derived from the DCE-MRI data. These parameters were then compared with presence of recurrence or metastasis, DFS and OS by using Cox regression (proportional hazards model) analysis, linear discriminant analysis.

Results

The results from of the 49 patients enrolled into the survival analysis demonstrated that traditional prognostic parameters (tumor size and nodal metastasis) and semi-quantitative parameters (E_max/1, and steepest slope) demonstrated significant differences in survival intervals (p < 0.05). Further Cox regression (proportional hazards model) survival analysis revealed that semi-quantitative parameters contributed the greatest prediction of both DFS, OS in the resulting models (for E_max/1: p = 0.013, hazard ratio 1.022; for stepest slope: p = 0.004, hazard ratio 1.584).

Conclusion

This study shows that DCE-MRI has utility predicting survival analysis with breast cancer patients.     

T1ρ and T2 mapping of the proximal tibiofibular joint in relation to aging and cartilage degeneration

Objective

To study the effects of aging and cartilage degeneration of the proximal tibiofibular- and femorotibial joint (PTFJ, FTJ) on the cartilage of the PTFJ using T₁ρ and T₂ mapping.

Materials and methods

We performed sagittal T₁ρ and T₂ mapping of the PTFJ and FTJ on 55 subjects with knee disorders. We placed 3 regions of interest (ROIs) on images of the cartilage in the PTFJ, medial femoral condyle (MFC), and medial tibia plateau (MTP). Correlation analysis was performed for the T₁ρ and T₂ values of each ROI and the patient age and the osteoarthritic grade of the PTFJ and FTJ.

Results

The T₁ρ and T₂ values of the PTFJ were affected neither by aging nor the osteoarthritic grade of the FTJ. Values of the FTJ normalized to PTFJ values were correlated with the osteoarthritic grade of the FTJ in the MFC (r = 0.851 and 0.779, respectively) and the MTP (r = 0.635 and 0.762, respectively). There was a significant difference in the T₁ρ but not the T₂ value of the PTFJ and MFC between normal and mildly osteoarthritic cartilage of each joint.

Conclusion

We document that the T₁ρ and T₂ values of PTFJ cartilage were not affected by aging or cartilage degeneration in the FTJ. The T₁ρ value of the PTFJ may represent a useful internal standard reference for evaluating early degeneration of the FTJ.     

Minor salivary gland tumors in the oral cavity: diagnostic value of dynamic contrast-enhanced MRI

Objective

To evaluate the diagnostic value of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) for minor salivary gland tumors in the oral cavity.

Materials and methods

Thirty-two patients with minor salivary gland tumors were examined preoperatively using DCE-MRI. Their maximum contrast index (CImax), time of CImax (Tmax), Tpeak; i.e., the time that corresponded to the CImax × 0.90, and washout ratios (WR300 and WR600) were determined from contrast index (CI) curves. We compared these parameters between benign and malignant tumors and among the different histopathological types of minor salivary gland tumors. Then, we categorized the patients’ CI curves into four patterns (gradual increase, rapid increase with high washout ratio, rapid increase with low washout, and flat).

Results

Statistically significant differences in Tmax (P = 0.004) and Tpeak (P = 0.002) were observed between the benign and malignant tumors. Regarding each histopathological tumor type, significant differences in Tmax (P < 0.001), Tpeak (P < 0.001), and WR600 (P = 0.026) were observed between the pleomorphic adenomas and mucoepidermoid carcinomas. It was difficult to distinguish between benign and malignant tumors using our CI curve classification because that two-thirds of the cases were classified into the same type (gradual increase).

Conclusion

The DCE-MRI parameters of minor salivary gland tumors contributed little to their differential diagnosis compared with those for major salivary gland tumors. During the diagnosis of minor salivary gland tumors, Tmax is useful for distinguishing between benign and malignant tumors.